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Twins or not twins?

Here`s a riddle:Two babies, a boy and a girl, were conceived 3 weeks apart and shared their mother`s womb for almost nine months and were born just a minute apart. Are they twins or are they not twins?

According to the Daily Mail and FoxNews, these UK-born babies aren’t actually twins because they weren’t conceived at the same time. The older sibling had a ?real? twin embryo which was lost just before the detection of the third younger embryo.

As a mom of twins (identical) who has done extensive reading on this topic, I would tend to disagree with this report. The Merriam Webster Dictionary defines a twin as ?either of two offspring produced at a birth? Another definition is that twins are 2 individual human beings who shared a uterus during pregnancy. Another term used for twins, triplets, etc. is multiple birth (vs. single birth), which literally means giving birth to multiple babies in one go. There is no mention whatsoever that they should have been conceived at the same time.
Non-identical or fraternal twins develop from 2 different eggs fertilized by 2 different sperms.
Usually, conception/fertilization occurs at around the same time. However, there are rare cases when the following could occur:

1. Superfecundation – 2 eggs are produced in 1 ovulation cycle are fertilized at different times (e.g. 2 sexual acts in closely succession) to produce 2 babies.

2. Superfetation – 2 eggs are produced in 2 different ovulation cycles and are fertilized at different times (e.g. 2 sexual acts weeks apart) to produce 2 babies.

These unusual occurrences have actually resulted in fraternal twins with different fathers! The case of the Mullineux babies in the UK is superfetation.

So what`s the answer to the riddle? I would say these 2 babies are twins. Before the days of ultrasound, they would have been labeled as twins and nobody would have known any better. So what do you think?

Test

Posted by Science-mom on Tuesday, January 15th, 2008 at 2:47 pm and is filed under Current Events, Twins.
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3 Responses to “Twins or not twins?”

I know where you are coming from. Someone I know was 18 weeks pregnant and then fell pregnant again, recently. She is currently 7 weeks or so into the other pregnancy. Quite a shock. But she’s excited about the new bub so all is cool. Pretty surprising what can happen in this world, huh?

I would agree that they are twins as well. My wife and I are expecting fraternal twins in May. As a result, I’ve been reading up on all things twin and am thoroughly amazed by them! The ultrasound shows that one is highly active while the other takes it easy. I am very interested to see if these traits remain in the kids through life. I’ll have to add this to my blog http://werehavingababies.blogspot.com